As described in German patent document 3,217,401 and in U.S. patent application Ser. Nos. 07/450,866 (now U.S. Pat. No. 5,069,254) and 07/498,586 (now U.S. Pat. No. 5,036,891) all of H. Vogelsang conduits assemblies are known comprising one or more tubes formed of a synthetic resin and interconnected transversely by longitudinally extending webs. Thus the tubes can be delivered rolled up on spools with the plurality of tubes and their webs in a flat coil. For use they are unwound, cut to length, and then bunched together to form the desired dense array of juxtaposed tubes through which electrical conductors, e.g. wires or cables, are pulled or pushed.
In order to facilitate insertion of the cables German patent document 3,529,541 of H. Vogelsang proposes forming the inner wall of each tube with longitudinally extending ridges alternating with longitudinally extending grooves. These longitudinally continuous and throughgoing formations reduce the contact area between the wires or cables being inserted through them to facilitate such insertion.
A major disadvantage of this arrangement is that the ridges invariably run somewhat along a helix like a screwthread due to the rotation of the worm in the extruder. These helically extending ridges impart some torsion to the electrical conductors being pushed or pulled through the conduit. Hence these conductors can twist up and get jammed, or can just wind about each other to form a bulkier mass than they actually need to.